This invention relates to semiconductor devices. More particularly, it relates to a power semiconductor device package and a method of making it.
It is well recognized that heat must be readily dissipated from a semiconductor device in order to ensure proper performance. This is especially true when the semiconductor device is a power device generally defined as those devices which dissipate one watt of power or more. It has been recognized that one method of removing the heat from the device is to include a heat sink in the package which houses the device.
Various methods have been employed to bond the semiconductor device to the heat sink. In one package design, the semiconductor device is bonded to a ceramic substrate, with the substrate in turn bonded to a metallic heat sink. Unfortunately, this intermediate ceramic substrate impedes heat dissipation for the device. Consequently, the heat generated in the device is not efficiently removed.
One of the other disadvantages of some of the commercially available packages is that they require relatively high temperatures in order to assemble the finished package. Some of these packages require a temperature of about 450.degree. F in order to assemble the package. Such high temperatures can degrade the performance of the semiconductor devices. This is especially true of MOS (metal-oxide-semiconductor devices.
In most applications, it is imperative that the package provide a good hermetic seal to protect the device from adverse environmental conditions. The prior art has heretofore provided such hermetically sealed packages only at the expense of additional cost in materials and labor.
It would be advantageous to provide a semiconductor device package which is low in cost and which can be easily assembled at temperatures which will not degrade device performance, while still providing excellent heat dissipation and hermeticity.